This invention relates to new polydentate salts prepared from polydentate phosphines containing at least two and preferably at least four trivalent phosphorus atoms or their antimony or arsenic analogs and their use in deactivating glass capillary columns for high temperature analysis of polar compounds via gas chromatographic techniques.
Gas chromatography techniques using glass capillary columns in conjunction with flame ionization detectors have developed as an analytical tool over the past two decades. Complex mixtures of hydrocarbons can be separated into their component parts using open tubular columns. The use of glass as a base material for capillary columns is advantageous because of its low catalytic activity and relative inertness to labile substances in complex mixtures. Such columns suffer from the disadvantage that components of polar mixtures are more strongly attached to the column wall. Thus, when the operating temperature is increased above 150.degree. C. the carrier gas tends to dislodge the column liquid phase from the glass surface causing decreased resolution by peak tailing.
This problem has been partly resolved by adding surface active material to the liquid coating phase to eliminate the effect of column wall. Various surfactants thus increased the useful operating temperature to about 170.degree. C. Other techniques (Metcalf, L.D. and Martin, R. J., Anal. Chem. 1204 [1967]) using trioctadecylmethylammonium bromide as an additive extended the useful temperature range of capillary columns to about 200.degree. C. By combining benzyltriphenylphosphonium chloride with various high temperature phases, Malec [J. Chromatog. Sci., 9, 319 (1971)] was successful in overcoming resolution difficulties and produced columns useful at about 250.degree. C. In the gas chromatographic analysis of polar mixtures, there is a need to provide capillary columns that will withstand even higher temperatures whereby substrate bleeding and peak tailing is eliminated using columns operated routinely at 300.degree. C. and above.